Rotary earth boring bit



Aug. 11, 1953 G. H. LANCHESTER ROTARY EARTH BORING BIT Filed Oct. 6,194'? INVENTOR George Herbert Lonchester ATTORNE YS Patented Aug. 111953 UNITED STATES PATENT OFFICE ROTARY EARTH BORING BIT ApplicationOctober 6, 1947, Serial No. 778,183 In Great Britain April 9, 1946 2Claims. 1

This invention relates to improvements in rotary earth boring bits andhas more particular reference to the type of bit for well drillingwherein multiple abrading or cutting wheels are rotated under pressureupon the work surface as the drill bit descends, and wherein a mud flushis led to the working face and the cutting tool in its rotationexcavates to its full diameter, the flush removing the eroded material.

Heretofore earth boring bits for oil wells and the like as set out aboveand particularly those of the multiple cutter head type have beenfashioned by dividing the bit stock into as many sections as the numberof cutters, each section carrying a stub axle and each such axle acutting tool. Equally each such cutting tool is provided with lookingball races and thrust roller bearings wherein the locking balls areinserted through passage ways extending from the exterior perimeter tothe race.

The provision of ball entrances to the cutting tool races tends toweaken the cross section of the stub axle, and the closure wall of eachpassage is continuously in abrasive contact with the wall of the wellbeing drilled.

The object of the present invention is to provide a multiple cutter bitwherein a divided cutter head is avoided with an increase of strengthand rigidity and wherein both ball and roller races are provided, thesaid balls for the bearings being introduced at the time of assemblywithout rollway passages for their entrance. A further object of theinvention is the easy removal and replacement of all or any of thecutters without disassembly of the whole cutter head or bit.

The invention consists in a rotary earth boring bit having a singlepiece housing centrally cored with threaded connection spigot andtapering sides, said housing accommodating a series of upwardlyconverging stationary stub shafts, all said shafts being secured withinsaid housing by a single locking member, each said shaft carrying anangularly disposed stub axle, said axle carrying a toothed cutter conerotatably mounted thereon but positionally locked thereto, and adaptedto abrasively contact the work surface upon rotation of the bit.

The invention is further characterized by means for circulating thelubricating flush that is brought to the work surface and its returnflow, said flush being introduced above the cone cutters and means forrotatably locking the cutter cones upon the stub axles and sealing thebearings against entry of dirt.

The races for'the balls of the ball bearings in the conical and toothedcutters are turned to running size but the entrance rims are left a fewthousandths of an inch less than the diameter for admission of theballs. The roller paths are turned to exact size and provision made fora sealing ring or rings. To assemble the bearings the axles with theballs and rollers are placed in position for entry and a cramping forceapplied from back to front.

The conical and toothed cutter is now heated externally by anyconvenient means causing expansion of the cutter shells until the ballspass the previously undersized rims and snap into the race, at whichpoint the heating means and cramps are withdrawn and the cutter shape incooling regains its intentional dimensions. When the balls are enteringwithin the respective races the movement of the stub axle to nest withinthe cutter shell also simultaneously locates the journal rollers whichare axially disposed and tends to close the cutter shell base upon thesealin ring or rings. A locating spigot formed at the end of the stubaxle enters a recess or socket in the cutter shell nose which aligns theinterengaging parts and has the further benefit of producing arelatively even thickness of cutter shell which is important forexpansion under heat when assembling the ball races, and for heattreatment when hardening.

In order that the invention shall be more fully understood anddescribed, reference is made to the accompanying drawings wherein athree cutter wheel assembly is shown and wherein:

Fig. 1 is a part sectional elevation of the assembled drill bit withthree toothed conical cutters,

Fig. 2 is a vertical elevation of stub shaft and axle m,

Fig. 3 is a vertical elevation of stub shaft and axle y,

Fig. 4 is a vertical part elevation of stub shaft for stub axle 2,

Fig. 5 is a plan of the bit head at line A-B, Fig. 1, and

Fig. 6 is a fragmentary front elevation showing one of the stub shaftsand its squared shoulders.

Referring to the drawings, and particularly to Fig. 1, the drill bithead I is formed as a steel housing internally cored at 2 and formedwith jointing shoulder 3, and normal screw thread and tapering couplingspigot 4. The housing has a grooved cylindrical skirt 5, and an upwardlytapering grooved contour above said skirt. The

housing I is bored angularly as at 6 to accommodate the three stationarystub shafts .r, y, and a, each said shaft having incised ports I for mudflush circulation to the cutting face from the passage 2, the latter ina known manner being in fluid circuit with a tubular drill string (notshown). The stub shafts m, y and z are held from downward displacementby the threaded bolt 8, whose head is accommodated in a recess 9 in thehousing I. The shank of the bolt engages grooves I in the shafts a: and:l/ but is threaded into a screwed aperture II in shaft 2. This assemblyrigidly locks the shafts :c, y, :c, in their upper parts but each saidshaft is provided with squared shoulders 12 which respectively engagerectangular sided bearing seats l3 in the housing :I The operative lowerend of the shafts :r, y, 2 have curved back shields I4 and an led emenions I5 of the shafts, said extensions carrying angled stub axles l6.Each stub axle l6 carries a boss H for seating a sealing ring IS, aroller path 19 and roller race seat 20 and below the latter a ball race2 [,each stub ax-le terminating in a locating spigot 22. Disposedu-ponthe stub axles are the cutter wheels 23. Said cutter wheels are formedas conical members of hardened steel, the angle of disposition of thestub axle to the common axis of the bit being such that the taper of theconical cutter used gives a substantially horizontal contact or that ofa flattened cone of the cutter wheel teeth 24 to the rock or earthdrilled. In the form shown stub shaft 2 carries a cutter wheel 23 havinga terminal cutter tooth or cone "bit 24a which projects beyond the axialcenter w of the drill bit. The object of this is to prevent conicalpiping at the well center face and obviate an undue side thrust whenboring very hard rock such as porphyry. The rows of teeth 24 of theseveral cutting heads 23 are staggered the one in relation to itsneighbors at cross planes where interference or jamming would Aotherwise occur at the lower series of toothed rings as shown in Fig. 1.Hence neither of the cutting wheels on stub axles of shafts :c and yareprovided with terminal cone bit teeth similar to tooth 24a, while theoutermost toothed ring 241) whose wear and stress is the greatest isclear of any contact with its neighbor wheels and are made of stoutsection and longer length of face. Ihe interior of the cutter wheelconical shells are each provided with a socket 25 for spigot 22 a ballrace 26 for the balls 21, the rim 28 of said race being turned to beless in diameter by say =7 or 8 thousandths of an inch than theoutermost limits of a confining circle of the assembled balls. Theremaining part of the cutter wheel interior has a truly turned rollerpath 29 and a recess 30 for the sealing ring 18, the back of the cuttershell just contacting the shoulder of the part 15 of stub shaft m, y, z.

The operation of the invention is as follows: Assuming the parts to beassembled as above described the drill bit as a whole is threaded to thetubular drill tube string and the bit and string lowered into operativeposition. The pressure due to gravity of the bit upon the workingsurface is adjusted by the operator. The mud lubricating flush is pumpedunder pressure down the string tube and enters the drill bit through thecore tube 2, passes through the passages TI and is fed to the cuttingtools through three equi-spaced tubular ports 31, the return circuit ofthe flush being external of the drill bit and through the passagesbetween the core cutters past the tapering sides of the bit housing 1,and through the annular passage existing between the well wall anddrilling tube string to the ground surface. the cutting drill bit isthen rotated and the teeth 24 cut or abrade the earth or rock surfaceand the respective toothed cutter cones are free to revolve. In somecases the teeth of the cutter cones 24 may be angled to increase dragcontact with the surface, and are preferably tipped with tungstencarbide, or other like hard and wear-resisting material. Since the teethof one cutter are staggered in relation to the others the whole circulararea of the work surface is traversed and the tooth 24a removes thecenter, this tooth under revolution of the whole cutter cone exertingthe maximum abrasive force. Although the invention has been described asapplied to a three cutter head bit, the invention is equallysatisfactory with a two cutter head or four.

According to the invention any one of the cutters and its stub shaft maybe removed and replaced without the slightest difficulty or great lossof time. To achieve this the bolt 8 is withdrawn, the particular stubshaft removed, a new one inserted and the bolt 8 replaced. This methodof replacement is of great advantage over some types of multiple cutterdrill bits wherein the housing is in the form of a multiple series ofcoupled parts each of which is an independent entity requiring exactalignment with the other-s in reassembly.

It will be understood that once the cutter cones 23 are in position uponthe stub axles, the stub shaft 9; or y or z and its stub axle I6 are inlocked relationship and cannot come adrift, the only means of removingand replacing the cutter cones 23 being to heat the cone about the ballrace 26 and rim e. g. by electrical means, and then pull the cone fromits axle I 6.

I claim:

1. A rotary earth boring bit comprising a shank with at least threebores converging upwardly from the base thereof and with a boreextending transversely of said shank near the upper ends of saidconverging bores, said transverse bore fully intersecting one of saidconverging bores and partially intersecting each of the remainingconverging bores, a stationary stub shaft remov ably mounted in each ofsaid converging bores, an angularly disposed stub axle secured to thelower end of each stub shaft, a rotary cutter cone mounted on each stubaxle, and a single locking member adapted to be secured in saidtransverse bore to look all said stub shafts in their respective bores,said single locking member having a threaded end, the stub shaft in saidfully intersected bore being formed with a threaded transverse holeadapted to receive the threaded end of said locking member, and theremaining stub shafts each being formed with a peripheral lock ingrecess to receive and fit around the body of the locking member in saidtransverse bore.

2. A rotary earth boring bit comprising a shank formed with at leastthree bores converging up.- wardly from the base thereof and with a boreex? tending transversely of said shank near the upper ends of saidconverging bores, a stationary stub shaft removably mounted in each ofsaid upwardly extending bores, each said stub shaft being formed nearits upper end with a locking recess, an angularly disposed stub axlesecured to the lower end of each said stub shaft, a rotary cutter conemounted on each said stub axle, and a single locking member adapted tobe secured in said transverse bore in locking relationship with thelocking recesses in said stub shafts, and thereby to look all said stubshafts in their respective 5 bores, in which the shank is provided witha centrally located mudfiush passage extending from its upper end to theupper end of the converging bores, in which each stationary stub shaftis provided with a mudfiush passage extending from its upper end, Whereit communicates with the mudflush passage in the shank, to a point aboutha1f way down the length of the stub shaft, and. in which the shank isfurther provided with an additional mudflush passage for each stubshaft, said additional mudfiush passages extending up- Wardly from thelower end of said shank to communicate each with the lower end of one ofsaid mudflush passages in said stub shafts, the lower ends of saidadditional mudfiush passages terminating just above said rotary cutters.

GEORGE HERBERT LANCHESTER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 829,634 Decker Aug. 28, 1906 Number Number

